This section provides background information to facilitate a better understanding of the various aspects of the disclosure. It should be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art.
Films and film laminates, i.e., multilayer films, based on polyvinyl chloride (PVC) or on thermoplastic polyolefins (TPO) or on polyurethanes (PU or PUR), are already well known from the prior art. They are used across a wide variety of different sectors, in the packaging industry, for example, or in the automobile sector. For use in the different sectors, particularly in the sector of automotive interior trim, the films or film laminates are further-processed by thermoforming operations or other deforming operations in order to obtain the desired form—for example; an automotive interior trim form. Exacting requirements are imposed on the films or film laminates in terms of their chemical and physical properties; for instance, grained films in particular are to have good grain stability and at the same time good scratch resistance. EP 1149858 A1 provides improved grain stability to a TPO film, for example, using electron beams. EP 1688460 B1 discloses a TPO film which in fact already has good grain stability but whose scratch resistance is inadequate. TPO films for the automobile interior typically exhibit much lower scratch resistance by comparison with PVC or PU films.
At the same time, attaining a gloss level of less than 1.5 after thermoforming is desirable, in order to achieve high-grade optical qualities for the film and to minimize reflections in windshields, for example. Reducing the gloss level is accomplished by introduction of a defined surface roughness and of the diffuse light scattering which this produces. The surface roughness is introduced in different lengthwise scaling. In general, the coarsest roughness with optical effect is introduced via the graining. The introduction of a finer roughness is accomplished usually by means of matting agents in the coating layer. Both measures together have, however, hitherto proven not to be enough to attain 1.5 gloss units after thermoforming. It is necessary, furthermore, for the film formula to exhibit a very fine surface roughness by virtue of its morphology. The contribution to roughness through the morphology of the film formula can be determined, independently of the graining and coating, directly on the thermoformed extruded specimen. Only if the extruded thermoformed specimen has a low gloss level can the coated grained component be expected to exhibit the required gloss level.